It's unclear what you're trying to acconplish, but if you expect XP Home
to give you fewer crashes than XP Professional, you're mistaken. They are
identical in stability; Professional just has a few extra features.
On the other hand, if you just want to install Home because you have a CD
for it, but not for Professional, you can do that. However there's no such
thing as uninstalling XP Professional. The only way to do what you want is
by doing a clean installation of XP Home, formatting the drive and
removing XP Professional along with everything else on the drive.
You can find detailed instructions here:
http://michaelstevenstech.com/cleanxpinstall.html
or here
http://windowsxp.mvps.org/XPClean.htm
or here
http://www.webtree.ca/windowsxp/clean_install.htm